When it comes to sustainability, it's hard to be the world's largest public corporation. It oftentimes means tripling or quadrupling the green efforts of other large corporations just to get the same results. And according to its 2009 Sustainability Report, Wal-Mart has some lofty aspirations, including a 100% renewable energy supply and a zero waste policy.

The company has a long way to go before achieving its goals, but Wal-Mart is making a surprising amount of progress for an institution that doesn't exactly specialize in local goods. While Wal-Mart only sources 1% of its power from renewable energy at the moment, it's still one of the largest solar installers in the U.S.--a point that, according to the Environmental Defense Fund's Gwen Ruta, highlights the "magnitude of the challenge facing both Wal-Mart and the country on renewable energy."

Wal-Mart has exhibited innovation in other areas has well. The corporation is working on organic clothing and food, sustainable seafood, fuel-efficient trucks, and building efficiency. Three prototype high-efficiency stores in Missouri, Illinois, and Texas were constructed using recycled building materials, use integrated water, heating and cooling systems, contain low-flow bathroom faucets, and have energy-efficient lighting. Wal-Mart has also succeeded in diverting 57% of waste generated in its U.S. stores from landfills.

But Wal-Mart has a long way to go before becoming a truly sustainable business. Total corporate CO2 emissions have increased over the past three years, and emissions will probably continue to grow as long as Wal-Mart keeps expanding. Since the chain is unlikely to stop opening up new stores, Ruta suggests that Wal-Mart would do well to pressure its supply chain into being sustainable. In other words, the company should take a systems thinking approach. If Wal-Mart's suppliers use sustainable practices (i.e. renewable energy, recyclable materials, etc.), then Wal-Mart's overall sustainability effort gains ground.

Related:
The Wal-Mart You Don't Know
The Fast Company 50 - 2009: #33 Wal-Mart
Environmental Activist Adam Werbach is Working With the Enemy--Wal-Mart

[Via EDF Innovation Exchange]